INVESTMENTS

The following table presents the amortized cost, gross unrealized gains and losses and fair value of securities available for sale and held to maturity:



	March 31, 2019
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	54,128	$	—	$	(347	)	$	53,781
Obligations of states and political subdivisions	114,770		2,218		(3		)	116,985
Agency mortgage-backed securities	895,899		6,461		(4,816		)	897,544
U.S. Treasury bills	9,964		113		—			10,077
Corporate debt securities	20,768		30		—			20,798
Total securities available for sale	$	1,095,529	$	8,822	$	(5,166	)	$	1,099,185
Held to maturity securities:
Obligations of states and political subdivisions	$	12,490	$	91	$	(20	)	$	12,561
Agency mortgage-backed securities	51,878		11		(303		)	51,586
Total securities held to maturity	$	64,368	$	102	$	(323	)	$	64,147



	December 31, 2018
(in thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
Available for sale securities:
Obligations of U.S. Government-sponsored enterprises	$	99,926	$	—	$	(1,428	)	$	98,498
Obligations of states and political subdivisions	26,566		327		(83		)	26,810
Agency mortgage-backed securities	596,825		1,160		(11,849		)	586,136
U.S. Treasury Bills	$	9,962	$	—	$	(37	)	$	9,925
Total securities available for sale	$	733,279	$	1,487	$	(13,397	)	$	721,369
Held to maturity securities:
Obligations of states and political subdivisions	$	12,506	$	16	$	(114	)	$	12,408
Agency mortgage-backed securities	53,173		—		(1,647		)	51,526
Total securities held to maturity	$	65,679	$	16	$	(1,761	)	$	63,934

At March 31, 2019, and December 31, 2018, there were no holdings of securities of any one issuer in an amount greater than 10% of shareholders’ equity, other than U.S. Government agencies and sponsored enterprises. The agency mortgage-backed securities are all issued by U.S. Government agencies and sponsored enterprises. Securities having a fair value of $478.8 million and $433.7 million at March 31, 2019, and December 31, 2018, respectively, were pledged as collateral to secure deposits of public institutions and for other purposes as required by law or contract provisions.

The amortized cost and estimated fair value of debt securities at March 31, 2019, by contractual maturity, are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties. The weighted average life of the mortgage-backed securities is approximately 4 years.



	Available for sale				Held to maturity
(in thousands)	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
Due in one year or less	$	1,876	$	1,888	$	—	$	—
Due after one year through five years	67,451		67,377		2,534		2,546
Due after five years through ten years	31,819		32,135		9,957		10,015
Due after ten years	98,484		100,241		—		—
Agency mortgage-backed securities	895,899		897,544		51,877		51,586
	$	1,095,529	$	1,099,185	$	64,368	$	64,147

The following table represents a summary of investment securities that had an unrealized loss:



	March 31, 2019
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government-sponsored enterprises	$	19,854	$	95	$	29,796	$	252	$	49,650	$	347
Obligations of states and political subdivisions	680		10		2,949		13		3,629		23
Agency mortgage-backed securities	47,506		685		326,319		4,434		373,825		5,119
	$	68,040	$	790	$	359,064	$	4,699	$	427,104	$	5,489

	December 31, 2018
	Less than 12 months				12 months or more				Total
(in thousands)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Obligations of U.S. Government-sponsored enterprises	$	19,622	$	322	$	78,876	$	1,106	$	98,498	$	1,428
Obligations of states and political subdivisions	3,102		15		14,156		182		17,258		197
Agency mortgage-backed securities	87,357		2,211		389,770		11,285		477,127		13,496
U.S. Treasury bills	—		—		9,925		37		9,925		37
	$	110,081	$	2,548	$	492,727	$	12,610	$	602,808	$	15,158

The unrealized losses at both March 31, 2019, and December 31, 2018, were primarily attributable to changes in market interest rates since the securities were purchased. Management systematically evaluates investment securities for other-than-temporary declines in fair value on a quarterly basis. This analysis requires management to consider various factors, which include among other considerations (1) the present value of the cash flows expected to be collected compared to the amortized cost of the security, (2) duration and magnitude of the decline in value, (3) the financial condition of the issuer or issuers, (4) structure of the security, and (5) the intent to sell the security or whether it is more likely than not the Company would be required to sell the security before its anticipated recovery in market value. At March 31, 2019, management performed its quarterly analysis of all securities with an unrealized loss and concluded no individual securities were other-than-temporarily impaired.